EP1094573A2 - Optischer Verstärker - Google Patents

Optischer Verstärker Download PDF

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Publication number
EP1094573A2
EP1094573A2 EP00122249A EP00122249A EP1094573A2 EP 1094573 A2 EP1094573 A2 EP 1094573A2 EP 00122249 A EP00122249 A EP 00122249A EP 00122249 A EP00122249 A EP 00122249A EP 1094573 A2 EP1094573 A2 EP 1094573A2
Authority
EP
European Patent Office
Prior art keywords
light
optical
optical amplifier
wavelength band
band
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00122249A
Other languages
English (en)
French (fr)
Other versions
EP1094573A3 (de
Inventor
Yasushi c/o Fujitsu Limited Sugaya
Hiroaki c/o Fujitsu Limited Tomofuji
Rikiya Fujitsu Hokkaido Dig. Tech. Ltd. Watanabe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fujitsu Ltd
Original Assignee
Fujitsu Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fujitsu Ltd filed Critical Fujitsu Ltd
Publication of EP1094573A2 publication Critical patent/EP1094573A2/de
Publication of EP1094573A3 publication Critical patent/EP1094573A3/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H01S3/06762—Fibre amplifiers having a specific amplification band
    • H01S3/06766—C-band amplifiers, i.e. amplification in the range of about 1530 nm to 1560 nm
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H01S3/06762—Fibre amplifiers having a specific amplification band
    • H01S3/0677—L-band amplifiers, i.e. amplification in the range of about 1560 nm to 1610 nm
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/1301—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers
    • H01S3/13013—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers by controlling the optical pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2383—Parallel arrangements
    • H01S3/2391—Parallel arrangements emitting at different wavelengths
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
    • H01S3/10015—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by monitoring or controlling, e.g. attenuating, the input signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2210/00—Indexing scheme relating to optical transmission systems
    • H04B2210/25—Distortion or dispersion compensation
    • H04B2210/258—Distortion or dispersion compensation treating each wavelength or wavelength band separately

Definitions

  • the present invention relates to an optical amplifier that reduces signal loss by reducing crosstalk.
  • WDM wavelength division multiplexing
  • an optical fiber amplifier is an essential device.
  • the present invention is applied to a structure of an optical amplifier to amplify a plurality of multiplexed bands. More specifically, the present invention allows the band of an optical amplifier to be widened.
  • FIG. 1 is a block diagram of a multiple-band-transmission system with a parallel amplifying structure, including a transmitting part 1-1 and a receiving part 1-2.
  • a demultiplex coupler 100 demultiplexes the C-band (1.53 to 1.56 ⁇ m) and the L-band (1. 57 to 1 .60 ⁇ m).
  • a multiplex coupler 200 multiplexes the C-band and L-band.
  • An optical amplifier 700 amplifies the C-band and an optical amplifier 800 amplifies the L-band.
  • the C-band output is in the range of 1.53 to 1.56 ⁇ m. Ideally, this output is at the port on the C-band side of optical amplifier 700, but when isolation for rejecting the L-band is set to a higher value, the insertion loss of demultiplex coupler 100 tends to become large and therefore loss of the signal transmitted (main signal light) becomes large, resulting in deterioration of an SN (signal to noise) ratio of the communication system as a whole.
  • crosstalk light If crosstalk light is occurred, it will result in detection level error in an optical input monitor located within optical amplifier 700 on the C-band side and optical amplifier 800 on the L-band side.
  • the control error may be occurred because an L-band optical light leaks toward the C-band side and a C-band light leaks toward the L-band side.
  • optical amplifier 700 we will discuss the case of AGC control as applied to optical amplifier 700, noting that the AGC control is performed in a similar manner at optical amplifier 800.
  • the optical power level of the exciting light source of optical amplifier 700 is controlled so that the gain becomes constant by detecting an input to output ratio.
  • the input light monitor of the optical amplifier 700 detects an input level in which a crosstalk light is added to the optical power of the wavelength band of the main element and the monitor of an output light of the optical amplifier 700 can neglect the crosstalk light because the optical amplifier 700 does not amplify the light outside the amplifying bandwidth.
  • shut-down detection when a shut-down detection is to be performed to prevent surge at the time of recovery by monitoring the input light and stopping pumping of optical amplifier 700 or fixing pumping to a particular value if there is no optical input, it may occur that the shut-down condition of the light cannot be detected due to the influence of the crosstalk light despite the fact that the light in the band of the optical amplifier 700 is shut-down. Moreover, such crosstalk may also be occurred in multiplex coupler 200.
  • the output of optical amplifier 700 is stopped or decreased by obtaining an amount of reflection with detection of the levels of the reflected light and output of light at the output of each optical amplifier 700,800 in order to determine a difference in reflection amount when the connectors are connected or when they are disconnected.
  • the connector opening detection threshold value is set to a value less than the amount of reflection.
  • the threshold value of the connector connecting condition is set higher than the maximum reflection amount.
  • the optical monitor for each band of the optical amplifier is given the characteristic rejecting the crosstalk light.
  • reject of the crosstalk light can be realized without increasing the loss of the main signal and accordingly the structure of the optical amplifier/repeater, which maintains the controllability of the optical amplifier without determining the signal characteristics, is realized.
  • Fig. 2 illustrates a multiple-band optical amplifier 10 according to a first embodiment of the present invention.
  • band demultiplex coupler 1 demultiplexes C-band and L-band and band multiplex coupler 2 multiplexes C-band and L-band.
  • First C-band optical amplifier 7 and first L-band optical amplifier 8 amplify C-band and L-band, respectively.
  • L-band rejection filters 771,772 and C-band rejection filters 871,872 filter C-band and L-band, respectively.
  • Optical receiving elements 791, 891, 792, 892, 793 and 893 monitor the optical powers respectively.
  • An optically multiplexed signal from a transmission line (not shown) is input to band demultiplex coupler 1 and is demultiplexed to the 1.53 to I 56 ⁇ m band of C-band and the 1.57 to 1.60 ⁇ m band of L-band and are respectively input to first C-band optical amplifier 7 and first L-band optical amplifier 8.
  • the optical branching coupler 751 within first C-band optical amplifier 7 branches a predetermined amount of C-band output of the bandwidth demultiplex coupler 1.
  • the branched output is filtered with L-band rejecting filter 771 for the purpose of rejecting the wavelength element other than the C-band.
  • Optical receiving element 791 (which may be a photodiode) monitors the C-band filtered light by detecting optical power of the C-band with rejection filter 771 and then inputs this optical power to control circuit 710.
  • the control circuit 710 is operated by AGC (auto gain controlling); receive a light power from optical receiving element 792 (which may be a photodiode) that is amplified by Erbium-doped fiber (EDF) of C-band and output lights of lasers 731,732; outputs of the lasers 731, 732 are adjusted to obtain a constant value of the ratio of optical receiving elements 791,792 and a pumping light is pumped for the EDF 711 for C-band with the WDM (wavelength division multiplex) couplers 741, 742.
  • AGC auto gain controlling
  • Optical demultiplex coupler 755 demultiplexes the light reflected from bandwidth multiplex coupler 2 and the light is then filtered with L-band rejection filter 772 and is then input to optical receiving element 793 (which may be a photodiode).
  • Control circuit 710 detects an amount of reflection light from the transmission line and a repeater (not shown) in the subsequent stage based on the ratio of an output of optical receiving element 793 and output to the band multiplex coupler 2 from optical demultiplex coupler 755 in order to control the optical output of C-band optical amplifier 7.
  • the output to band multiplex coupler 2 from optical demultiplex coupler 755 is known from the value of optical receiving element 792.
  • Second C-band optical amplifier 78 and variable attenuator 76 are optionally provided.
  • An output of the multiple band optical amplifier 10 is controlled to adjust (equalize) the gain for each wavelength under automatic level control (ALC).
  • ALC automatic level control
  • Second C-band optical amplifier 78 usually performs the AGC control and the light is input to second C-band optical amplifier 78 in order to always make constant the output of second C-band optical amplifier 78 which is controlled with variable attenuator 76.
  • the elements corresponding to the first C-band optical amplifier 7 in the first L-band optical amplifier 8 are designated with the same reference numbers except for the first digit and like elements perform like operations.
  • lasers 731, 732, 831, 832 produce a laser light having a wavelength of 0.98 ⁇ m or 1.48 ⁇ m.
  • operations are possible only with forward pumping of the lasers 731, 831 or alternatively with backward pumping of lasers 732, 832.
  • Control circuits 710, 810 have been explained with respect to AGC control, shut-down detection and backward monitoring. Moreover these control circuits may also be adapted to ALC control using an input monitor value.
  • band rejection filters 771, 871, 772, 872 are capable of transmitting one band and rejecting the other bandwidth.
  • this rejection characteristic is sufficient, the characteristic specification of crosstalk between bands of the band demultiplex coupler 1 is alleviated to reduce the loss of the main signal.
  • each band is amplified with the optical amplifiers of two stages, if the gain is not corrected accurately in the preceding stage, an output deviation becomes large if gain tilt is generated after the output level becomes high in the subsequent stage. Therefore, it is necessary to accurately monitor the light in the band that is amplified with the optical amplifier.
  • the respective band rejection filter When one isolation is neglected in the band demultiplex coupler 1, it is enough for the respective band rejection filter to have only one band. For example, if isolation in the C-band side of the band demultiplex coupler 1 is raised, the L-band rejection filter 771 is no longer required and only the C-band rejection filter 871 is required. Moreover, if isolation on the C-band side of bandwidth multiplex coupler 2 is raised, L-band rejection filter 772 is no longer required and only C-band rejection filter 872 is required. However, at the time of amplification, it must be considered that if isolation is increased, loss becomes high.
  • Fig. 2 illustrates a structure which is applied to an inline amplifier.
  • band demultiplex coupler 1 When this structure is used in a post-amplifier, band demultiplex coupler 1, and rejection filters 771, 871 are omitted.
  • the band multiplex coupler 2 and rejection filters 772, 872 are not used. This is also true of the second and fourth embodiments.
  • Fig. 4 illustrates a multiple band optical amplifier 20 according to a second embodiment of the present invention.
  • Multiple band optical amplifier 20 differs from multiple band optical amplifier 10 of FIG. 2 in that the function of a band rejection filter (not shown) is provided inside the optical coupler and individual band rejection filters 771, 871 are therefore not needed.
  • the other elements are identical to multiple band optical amplifier 10 of Fig. 2.
  • WDM coupler 743 for demultipexing only a part of the C-band wavelength is provided on the output of the C-band side of the band demultiplex coupler 1.
  • WDM coupler 744 for multiplexing only a part of the C-band wavelength is also provided to the optical receiving element 791 for monitoring the emitted light in the C-band side of the band multiplex coupler 2.
  • FIG. 5 illustrates a third embodiment of the present invention.
  • band rejection filters 745,845 which perform a function similar to that of rejection filters 771, 772, 871, 872 and WDM couplers 743, 843.
  • Band rejection filters 745, 845 are designed to provide a smooth characteristic, as illustrated in FIG. 6.
  • the amount of rejecting the crosstalk light through the band rejection filters 745, 845 is not required to be rejected perfectly in relation to the predetermined band, and is effective only by rejecting the predetermined amount of the total power.
  • any filter which is designed to show such a smooth characteristic as illustrated in Fig. 6, sufficiently functions if it can reject the predetermined amount of total power in the predetermined band.
  • Fig. 7 illustrates a multiple band optical amplifier 30 according to a fourth embodiment of the present invention.
  • the embodiment of Fig. 7 has a structure for electrically correcting a processor function that calculates, after detecting the receiving optical level in the optical receiving elements 791, 891, 793, 893, respectively, the incident crosstalk light level from the assumed crosstalk of the band demultiplex coupler 1 and band multiplex coupler 2 and the optical receiving level of the other band, and then uses the optical receiving level after subtraction of such incident crosstalk light level as the optical input level.
  • L L , L C , I CL , I LC are determined uniquely depending on the bandwidth of demultiplex coupler 1 and the bandwidth of multiplex coupler 2. Therefore, the true L-band value P L and true C-band value P C can be obtained by detecting P inL and P inC and then calculating these values by the equations (1) and (2).
  • processor circuit 91 satisfying the above equations is provided to conduct the calculation on the basis of the outputs of optical receiving elements 791, 891 and then the true L-band value P L and true C-band value P C which have been obtained by electrically correcting the error due to crosstalk of the band demultiplex coupler 1 are input to the control circuits 710 and 810. Thereby, control circuits 710, 810 can execute the predetermined control explained in regard to the first embodiment.
  • control circuits 710, 810 can also execute the predetermined controls by providing processor circuit 92 satisfying the above equations to calculate outputs of optical receiving elements 793, 893 and then respectively inputting the true C-band value and L-band value to the control circuits 710 and 810 obtained by electrically correcting the error due to crosstalk data of the band multiplex coupler 2.
  • the present invention can prevent control error due to the crosstalk between the bands occurring in the multiple bandwidth optical fiber amplifier without deterioration of characteristic of the main signal.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)
  • Lasers (AREA)
  • Optical Integrated Circuits (AREA)
EP00122249A 1999-10-18 2000-10-18 Optischer Verstärker Withdrawn EP1094573A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP29566199 1999-10-18
JP29566199A JP4013425B2 (ja) 1999-10-18 1999-10-18 複数波長帯域光増幅器

Publications (2)

Publication Number Publication Date
EP1094573A2 true EP1094573A2 (de) 2001-04-25
EP1094573A3 EP1094573A3 (de) 2003-11-19

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EP00122249A Withdrawn EP1094573A3 (de) 1999-10-18 2000-10-18 Optischer Verstärker

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US (1) US6483636B1 (de)
EP (1) EP1094573A3 (de)
JP (1) JP4013425B2 (de)

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JP4821037B2 (ja) * 2000-08-25 2011-11-24 富士通株式会社 ラマン増幅を用いた光増幅器およびラマン励起光源
US7106969B1 (en) * 2001-02-12 2006-09-12 Atrica Israel Ltd. Optical network terminator
US6671085B2 (en) * 2001-04-11 2003-12-30 Bti Photonics Inc. Switchable dynamic gain-flattened optical amplifiers and methods with wide dynamic gain range
KR100405817B1 (ko) * 2001-04-16 2003-11-14 한국과학기술원 광대역 광증폭기
US6697193B1 (en) 2001-06-06 2004-02-24 Cisco Technology, Inc. Shared variable gain amplifier for WDM channel equalization
US6954305B2 (en) * 2001-09-26 2005-10-11 Sumitomo Electric Industries, Ltd. Optical amplifier and optical transmission system using it
US7196840B2 (en) * 2001-11-29 2007-03-27 Broadband Royalty Corporation Amplitude balancing for multilevel signal transmission
JP4128356B2 (ja) * 2001-12-28 2008-07-30 富士通株式会社 光デバイスの制御装置
KR100407326B1 (ko) * 2002-02-27 2003-11-28 삼성전자주식회사 밴드 간섭을 최소화한 광대역 어븀첨가 광섬유 증폭기
US7075712B2 (en) * 2002-05-30 2006-07-11 Fujitsu Limited Combining and distributing amplifiers for optical network and method
US6980357B2 (en) * 2004-02-13 2005-12-27 General Instrument Corporation Optical amplifier apparatus and method
JP4941017B2 (ja) * 2007-03-09 2012-05-30 日本電気株式会社 光アンプ、その制御装置、制御回路、制御方法及び制御プログラム並びに光通信ネットワーク
WO2014090278A1 (en) * 2012-12-10 2014-06-19 Telefonaktiebolaget L M Ericsson (Publ) Power control in bidirectional wdm optical link
US10340649B2 (en) * 2017-03-07 2019-07-02 Nec Corporation C-band and L band amplifier design with increased power efficiency and reduced complexity
WO2019168099A1 (ja) * 2018-03-02 2019-09-06 日本電気株式会社 光中継器、伝送路ファイバの監視方法、及び光伝送システム
US11271670B1 (en) * 2020-11-17 2022-03-08 Cox Communications, Inc. C and L band optical communications module link extender, and related systems and methods

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JP3288965B2 (ja) 1996-12-11 2002-06-04 日本電信電話株式会社 光ファイバ増幅器および光増幅方法
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Title
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Also Published As

Publication number Publication date
JP2001119351A (ja) 2001-04-27
EP1094573A3 (de) 2003-11-19
US6483636B1 (en) 2002-11-19
JP4013425B2 (ja) 2007-11-28

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